The invention relates to a device for moving a working means in the ground, comprising a push-pull unit for generating a linear movement of a working means connected to the push-pull unit via a rod assembly. A device of this type can, for example, be used for replacing supply pipes which are laid underground. For this purpose, a tool destroying the old pipe and/or an expansion head is connected as a working means to the end of the rod assembly remote from the device. This working means is pulled into the ground together with a new pipe section upon retraction of the rod assembly. Such an arrangement and a device suitable for driving the rod assembly are, for example, known from the document DE 103 32 328 B3. This known device comprises an automatic clamping device with two clamping jaws for establishing a working connection between the push-pull unit and the rod assembly. The clamping jaws are each mounted so as to be pivotable about a journal. The rod assembly can be clamped between the clamping jaws upon a driving motion of the push-pull unit. In this process, the automatic clamping device clamps the rod assembly in one working direction. The clamping device is formed such that, for changing the working direction, it is reversible and thus selectively causes a feed or a retraction of the rod assembly. In the direction of motion opposite to the working direction, the clamping device is movable freely relative to the rod assembly.
With the aid of the clamping device a mere non-positive connection is established between the clamping device and the rod assembly. In particular, if the rod assembly and/or the clamping jaws get dirty when used on a construction site, the contact force of the clamping jaws on the rod assembly upon clamping of the rod assembly might be reduced so that a slipping of the rod assembly through the clamping jaws in the clamped state cannot be reliably prevented.
From the document DE 196 08 980 C2, a device for drilling in the ground is known, in which a coupling is provided between a push-pull unit and a rod assembly via coupling means which engage in a form-fitting manner with projections or into recesses of the rod assembly. Here, it is provided that a ratchet which is used as a coupling means engages behind a projection or in a recess. As a result thereof, the entire feed force to be introduced into the rod assembly is introduced via the form-fitting coupling means. For this, both the ratchet and a pivot pin for the pivotal arrangement of the ratchet as well as the recesses or, respectively, the projections have to be dimensioned relatively large so that the coupling means can introduce the required feed force into the rod assembly. In particular under construction site conditions, the coupling means as well as the projections or, respectively, recesses can get dirty, which reduces the engagement areas for the engagement of the coupling means. Thus, there is a risk that no reliable form-fitting connection can be established between the coupling means and the rod assembly. In particular, the coupling means can slip out of a dirty area of engagement formed by the projection or the recess in the rod assembly. In particular, it is possible that high mechanical stresses occur due to the small transmission surface and, as a result thereof, damages to the rod assembly and/or the coupling means can be caused. Further, for a form-fitting coupling relatively large projections or recesses must be provided, as a result whereof a relatively large total cross-section of the rod assembly is necessary. The total push and pull forces exerted on the rod assembly have to be transmitted by the rod assembly cross-section remaining in the area of the recesses or, respectively, by the rod assembly cross-section outside of the projections.
In the devices known from the documents DE 103 32 328 B3 and DE 196 08 980 C2 rod assemblies can be used which are assembled from individual rod members or are formed as a link chain. Further, the known devices can be arranged in pits which are placed in the ground. With the aid of the device the rod assembly can then be pushed into a supply pipe, which is preferably to be renewed and which ends in the pit, until an end region of the rod assembly projects from the supply pipe at the other end thereof. A working means and preferably a supply pipe to be pulled in can then be connected to this end. With the aid of the device, then the rod assembly together with the working means and the new supply pipe to be pulled in is pulled through the old supply pipe. In doing so, the old supply pipe is preferably destroyed, the area around the old supply pipe is expanded and the new supply pipe is pulled into the expanded area.